Process of desiccating the solid content of milk.



W. H. SWENAETON. PROCESS OF DESIOGATING THE SOLID CONTENT OF MILK.

APPLICATION FILED JAN.18, 1906.

Eat-aimed Jun-a 13, 191i.

2 SEEEIS-SHEET l.

Wzfmetiseax u iia.

5 W, H. SWBNARTON.

PROCESS OF DESIGUATING THE SOLID CONTENT OF MILK.

APPLICATION FILED JAN.13,1906.

@Qfififi Patented June 13,1911.

2 SHEETS-SHEET 2.

WAI'IS'IILL ,H. SWEITABTON, O1!" MOR'I'CLAIR, PROCESS O! DEBICCATING THE SOLID,

Specification of Letters Patent. Application filed January 13, 1906. Serial No. 296,886.

new JERSEY.

com-mm or mm.

Patented June 13, 1911.

To all whom. it may concern:

Be it known that I, WAITS'I'ILL H. SWE- NAR'ION, a citizen of the United States, residing at Montclair, in the county of Essex and State of New Jersey, have invented certa'in new and useful Improvements in Processes of Desiccating the Solid Content of Milk, of which the following is a specification.

My invention relates to the desiccation of milk and has for its object the separation of the milk-solids in the form of a. fluffy, flaky powder, which upon the additionof warm water thereto will readily dissolve and emulsify to form a liquid having all the propertics of normal milk. These objects I attain by delivering a mass of homogeneouslyconccntrated milk, free from unconcentratcd portions in the form of a thin layer or sheet, to moving heated surfaces initially heated in excess of five (5) degrees centigrade above the boiling point of the milk at the pressures at which the operation is performed. The layer is cooled during the formation of the same by the inflowing milk in its passage to the receiving receptacle, but without direct contact therewith and is removed in the form of a self-sustaining mass having the identity of a film from the heating surface prior to the complete evaporation of the water therefrom and while still possessing a slightly moist appearance.

Milk has long been considered a typical emulsion, and naturally the casein, which is the rincipal proteid constituent, exists in the orm of what has been termed a di-calcium caseinate which, owing to its atlinity for water, is in a highly swollen state. If the so-called poise of the calcium caseinate molecule is affected, either by protractedheating at those temperatures at which the calcium salts precipitate, or by excessive drying, the calcium caseinate loses to a greater or less extent this afiinity for water and therefore the formation of a perfect emulsion upon the addition of warm water to the dry product, no longer results. Besides casein, milk and especially skim-milk,

contains, in almost equal amounts, lactose or milk-sugar. This milk-sugar normally crystallizes with one molecule of water Although this water is not yielded up after crystallization has taken place until the temperature reaches about 140 0., nevertheless prior to such crystallization, the water present in which the milk-sugar is dissolved, may be entirely evaporated at temperatures much below 140 (3., and these temperatures approximate the boiling point of water at the pressure at which the process is performed. Then again milk-sugar caramelizes when heated in the air and in a concentrated condition. At high temperatures also the air has an energetic action upon the same and renders it very diiiicultly soluble. The well known skin which forms when milk is-heated in the air for protracted periods even at the boiling point illustrates the above noted changes in the casein and milk sugar due to protracted heating in the air. The proper treatment of the two ingredients above noted, therefore, is the crux of all drying processes.

Heretofore in desiccating milk in vacuo, to which method of drying my process par ticularly relates, the temperatures used have been such that the heating surface or roll was maintained at and even in rare instances above the boiling point of the liquid in the mono maintained, but in each instance, either the temperature of the medium used to heat the surface or roll, which temperature is approximately indicated by the initial temperature of the roll, was less than five (5) degrees Centigrade above the boiling point of the particular oacuo maintained, or again in cases where the temperature was sufficiently high, the method of delivering the milk to the heating surface was such that an unequal and non-homogeneous layer was deposited upon said rolls. In the former process, owing to the considerable cooling efi'ect of the large body of inflowing unconcentrated liquid in the retaining pocket or receptacle, the temperature of the heating surface falls to such an extent that the immediate vaporization of the water in the layer (as distinguished from immediate boiling), fails to occur and hence in lieu of heating the film while revolving the heating-rolls in ten second periods, as is the case in my process as hereinafter described, in many cases but one revolution in forty-five seconds occurs, with the results due to prolonged heating heretofore noted. In the latter process, since a thin layer of unconcentrated liquid naturally required less time to dry than a thick layer of concentrated liquid, the process was impracticable because exact regulation of the drying period in to high temperatures order to obtain a uniform product was obviously impossible. In neither of the above cases moreover was any allowance made for the live per cent. of water which the molecule of milk sugar is capable of chemically uniting with, but the milk was reduced to complete or bone dryness as 15 borne out by the reference in the cases to subsequent grinding in a pebble mill or otherwise in order to produce an impalpable powder wlnch could thus offer the largest possible surface to any liquid added thereto. These products, however, notwithstanding their impalpable condition, were granular and failed to emulsify in a satisfactory manner upon the addition of warm water thereto, and in no instance was the temperature of the heating surface sufiieiently high to produce a sterile milk powder, 2'. 0. above 75 C., as although many disease producing bacteria are destroyed when temperatures of from C. to C. are maintained for periods extending over several minutes, a momentary heating period requires a higher temperature for the destruction of the bacteria and in both cases a temperature in excess of C. is required to destroy the spores which in certain instances even multiply at 70 C. Owing to the violent agitation and thorough heating of every particle of the milk, even momentary heating above 75 C. serves in my process to destroy substantially all deleterious bacteria.

Having thus indicated the nature and object of my process, and in order to enable those skilled in the art to practice the same, I will now proceed to describe my preferred mode of performing it, reference being had to the apparatus disclosed in the accompanying drawings, forming a. part of this specification.

Like reference numerals are used to designate like parts throughout and in both the specification and claims I include under the term milk various lacteal liquids having similar properties, such as normal milk,-

skim-milk, modified milk, etc. Owing to the analogous properties possessed by solutions of casein, a derivative of milk, I consider the treatment of the same according to the herein described process, to be equally within the spirit of my invention.

In the accompanying drawings: Figure 1 is a longitudinal elevation chiefly in section. Fig. 2 is a longitudinal elevation chiefly in section of a single cylinder evaporator, showing the method of delivering the milk and simultaneously cooling the forming film. Fig. 3 is a plan view of the distributer, isolated, and Fig. 4.- is a similar view of v a modification, both views being along lines corresponding to line 34 of Fig. 2.

Referring to the drawings, the numeral 1 designates the supply pipe which is in communication with a reservoir (not shown). The pipe is provided with a valve 2 and a nozzle 3, which aflord communication with a distributer 4. Adjustable conical valves 0 on stems 5 serve to accurately regulate the supply of liquid to the cylinders 7. A vacuum-pan casing 8 envelops the cylinders and the vapors are drawn oflI' therefrom through an outlet 9 to a condenser (not shown). Adjustable doctors or knives 10 are connected with the casing and suitable observation windows 11 are provided. A rotatable wiper 19. operated by a button 13, serves to remove deposited mist from said windows. Within the apparatus is arranged a lamp 14 which permits of observation of the film during evaporation of the same. The casing is provided on opposite sides with chutes 15 which terminate in air locks 17, comprising the valves 10, the bottoms 18 and the exhaust. cocks 19. A pipe 20 serves to supply suitable heating mediums to the cylinders, such for example as exhaust water from a condenser mingled with the amount of steam necessary to produce the desired temperature, or exhaust steam from a condenser may be advantageously utilized in lieu of said mixture of live steam and hot water. If desired a partial vcrcuo can be established in the interior of said cylinders, when using hot water, in order to convert the same into low pressure steam and secure increased thermal efficiency. Moreover various constructions may be adopted for saideylinders in order to efiiciently heat the same, such for example as those disclosed in the patents to Pass burg #830,521 of September 11, 1900 (filed July 27, 1905), and to Ekenberg, #764,995 of July 12, 1904, all without departing from the spirit of my invention. In Fig. 2 the numeral 1 represents the supply pipe which is in communication with a reservolr (not shown) and may be arranged to permit of gravity feed of the milk in lieu of the customary forced feed, if desired. A distributer 4 is extended at the bottom in the form of an are which may if desired possess aradius equal to that of the abutting cylinder and is preferably of nickel steel. A supply pipe 1 is connected with the arc-like extension distant from the cylinder and adjustable conical valves 6, on stems 5, serve to regulate the supply of milk to the retaining pocket formed between the distributer and the abutting cylinder 7. A doctor 10 serves to remove the tenacious film from the cylinder when the same is revolv-' ing in the direction indicated by the arrow.

In Fig. 4 the numerals 4' designate the extended portions of the bottom of the distributer which serve to feed liquid from the pipe 1 to the abbreviated arc-like extension of the bottom of the distributer 4:.

The operation of my process as preferably carried out, is as follows: The milk is perature of the cylinder in my preferred process, corresponds to the ratio e. e. the boiling point of the vacuum maintained is 82.5% of the temperature of the heating medium of said cylinder, although it is obvious, since the milk must be dried during a portion of a revolution, that if the layer were of excessive thickness, the substantial reduction of said layer to a selfsustaining film will not occur with in a single revolution unless the difference between the boiling'point of the vacuo and the temperature of the heating surface in such cases is somewhat greater than Ihis can of course be readily determined by trial when the necessit therefor arises.

The boiling points of milk in any particular cameo can be readily determined either by actual measurement or more expeditiously, by reference to physico-chemical tables, relating to the boiling points of water at different sub-atmospheric pressures, since their boiling' points for all practical purposes are substantially identical. The following approximate data, have been taken from such a table:

Vacuum. Boiling point of milk. 12.7 cm 90.5degrees C. --25.4 cm 85.0

In order to produce a sterile milk powder, the milk is delivered onto cylinders, heated for example to 98 C. and a 'vacuo corresponding to a boiling point of 82.5% of 98 or 81 C. is maintained. If a temperature, suflicient to destroy the developed bacteria and not the spores is used, as for example 75 C., then a mono of 54,5 cm. is preferably maintained. If it be desired to produce a so-called milk-powder capable of reproducing a, solution in which lactic acid fermentation progresses on standing, in a manner similar to that in the case of normal milk, and which solution will be readily peptonized by rennet, I referably heat the cylinder to 54.5 C. w1ile maintaining a ware .0 corresponding to 45 C. 01' as given in the above table 68.6 cm.

In order to eliminate the Well known skin formed by the action of air at high temperatures upon the casein, milk-sugar and various salts normally found in milk, and which skin causes the occlusion of the steam with a consequential protracted heating of the milk solids, whether evaporating under low oacuo or in the open air, I have discovered an economical and effective method whereby the layer while forming, is maintained below the temperature at which the said deleterious action occurs, or as it may be termed, the critical temperature, and the heat so abstracted is conserved and utilized to heat the inflowing milk in its passage to the retaining pocket. This cooling effect, I accomplish as illustrated in Fig. 2, by causing the milk in its passage from the reservoir to the distributer, to expand into a thin layer or sheet, and ,to contact with. the opposite surface of the nipping or film-forming wall from that in contact with the concentrated milk in the retaining pocket and adjacent the area Where the formation of said film occurs. The bottom of the distributer, as shown, is extended in the form of an arc, and preferably has an internal dimension, transversely of the cylinder and at a point adjacent thereto, of from 1.5 to 2.5 cm.', whereby a continuous sheet of milk of the above depth may be caused to cool the forming layer. may be either extended along the entire length, or it may be extended at intervals along the same without departing from the spirit of my invention which includes any method of transference of the heat from the .layer while forming to inflowing milkin its passage to the retaining pocket. Since the inner surface of the distributor merges into that of the extension in a continuous curve it is perfectly smooth with the result that circulation of milk along the same is entirely unimpeded. In practice my dis tributer is provided with extremely thin walls in order to effect the greatest amount of cooling of the layer and suitable adjusting means may if desired be provided, whereby the distance of the distributer from the cylinder may be accurately regulated.

lVhichever one of the above methods of feeding the milk is selected is immaterial in so far as the next stage of the process is concerned, as the water in the milk. upon contact with the highly heated cylinders (highly heated with respect to the cacao) is immediately vaporized and unless the milk in the form of a self-sustaining mass having the identity of a film is almost instantly removed therefrom while still slightly moist and tenacious, the water of crystallization, which serves as a margin of safety, so to speak, is evaporated with the resultant destruction of the" desired properties heretofore noted. In practice the film is removed while still possessing a slightly The bottom of said distributer I moist appearance and while retaining sufiicient water to possess when cool a moisture content in excess of 1% and in the case of milk consistin of 7} whole milk and skimmilk the pow er should contain from 2% to 4% of moisture. On cooling a film containing the minimum amount of moisture stated, the chemical and physical absorption of water occurs with the. production of a perfectly dry powder, which owing to the entire a sence of caking while evaporating, readily disintegrates and may be sifted to a. li ht, fiufi'y, flaky powder approximating G. without resorting to grinding as is customary in other 'vacuo processes. Moreover, owing to the presence in said product of the casein, milk-sugar, lact-albu- 4min and other non-fatty ingredients thereof, in their natural and unaltered condition,

the said product can be readily emulsified with cold water and a liquid is obtained which has a natural milk-like odor and appearance and is substantially free from any burnt or boiled flavor due to the presence of caramelized milk sugar, altered casein, or altered lact-albumin. Naturally a certain amount of the moisture in the moist film, in addition to that which is absorbed, will be driven off by the normal evaporation during the passage of the film into the receptacle or chamber arranged to receive the same. Moreover, since said chamber is heated by the radiation and conduction of heat from the evaporating chamber as herein provided for, (or, if desired, by supplement-a1 heating means of any desired type) additional moisture will continue to evaporate from the film after entering said receptacle, until nothing but the fluff powder remains. A speed -of six revo utions pr'minute as against one revolution in 45 seconds, customary in'another well known cacao process, can be maintained in my process and in practice the size of the rolls is such that this speed is equivalent to a peripheral speed of 14 meters per minute.

As I am not the first-inventor thereof, I disclaim the invention covered by'the following counts 1. The process of desiccating milk which consists in rapidly partially condensing the same under diminished atmospheric pressureat a temperature below 212 F., with-' contact with heated surfaces maintained at a temperature below 212 F. but sufiiciently high to produce almost immediate violent ebullition of the whole volume of the milk,

withdrawing the partially condensed material from the bottom of the mass in the form of thin layers or films upon moving rollers and subjecting the same to heat at a temperature below 212 F., under diminished atmospheric pressure.

It is not desired to claim in this application any process not carried out in a wacuo, or any product not produced by a vacuo process, and applicant specifically disclaims any and all products not produced in vacuo, but by processes carried out under normal or super-normal atmospheric pressures.

It is evident that when the layer of milk is cooled, while forming by iuflowing milk, 'as herein described, it will froth considerably under the reduced pressure in the auxiliary receptacle prior to its escape through the outlet thereof, and prior to its coming in direct contact with the excessively heated evaporating roll, and that accordingly the frothing will be less than were the milk subjected, in the form of a thin layer, to an ex cessive temperature with respect to the boiling point of the uacuo, immediately upon it being subjected to the reduced atmosphere pressure.

The word film as employed in the claims is used to designate the self-sustaining mass which results from the evaporization of the greater portion of the liquid from the milk as the same is removed from the evaporating surface, this term being used to distinguish it from an amorphous slime from which it is as diflicult to entirely remove the remaining liquid as it would be from an original milk solution.

Having thus described my invention, what I claim 13:

1. In the process of desiccating the solidcontent of milk, the steps which consist in delivering a mass of milk onto a surface in 'vacuo heated in excess of five degrees centigrade above the boiling point of the milk in said vacuo, heating said mass 'for a period of ten seconds or less, and then removing said milk in the form of a self-sustaining mass having the identity of a film from said surface in such a condition that it has a moist appearance and its moisture-content when dry and cool is in excess of one and one-half per cent.

2. In the process of desiccating the solidcontent of milk, the steps which consist in delivering a mass of milk onto an evaporating surface in 'vacuo heatedin excess of five degrees centigrade above the boiling. point of the cacao, and then removing said milk in the form of a self sustaining mass having the identity'of a film in such a condition that it has a moist appearance, and its moisture-content when dry and cool is in excess of one and one-half per cent.

3. In the process of desiccating the solidcontent of milk, the steps which consist in delivering a mass of milk onto an evaporating surface in mono heated in excess of five degrees centigrade above the boiling point of the mono, and then removing said milk in the form of a self-sustaining mass having the identity of a film from said surface while in such a condition that it has a moist appearance and its moisture-content when dry and cool is between two and one-half and four per cent.

t. In the process of desiccating the solid content of milk, the steps which consist in delivering a mass of milk onto an evaporating surface in mono heated in excess of five degrees centigrade above the boiling point of the cacao, andthen removing the said milk in the form of a self-sustaining mass having the identity of a film from said surface while in such a condition that it has a moist appearance and its moisture content when dry and cool is between one and onehalf and five and one-half per cent.

5. In the process of desiccating the solidcontentof milk, the steps which consist in delivering a mass of milk onto an evaporating surface in vacuo heated in excess of five degrees centigrade above the boiling point of the mono and in excess of sevent '-five degrees centigrade, and then removing the said milk in the form of a self-sustalning mass having the identity of a film from said surface while in such a condition that it has a moist appearance and its moisture-content when dry and cool is between one and onehalf and five and one-half per cent.

6. In the process of desiccating the solidcontent of milk, the steps which consist in delivering a mass of milk onto an evaporating surface in vacuo heated in excess of five degrees centigrade above the boiling point of the ammo, and in excess of ninety degrees centigrade, and then removing said milk in the form of a self-sustaining mass having the identity of a film from said surface while in such a condition that it has a moist appearance and its moisture-content when dry and cool is between one and one-half and five and one-half per cent.

7. In the process of desiccating the solidcontent of milk, the steps which consist in delivering a mass of milk onto an evaporating surface in oacuo heated in exfrom said surface while ninety-five degrees centigrade' and then re moving the said milkin the form of a self sustaining mass having the identity of a film from said surface while in such a condition that it has a moist appearance and its moisture-content when'dry and cool is between two and one-half and five and onehalf er cent.

8. n the process of desiccating the solidcontent of milk, the steps which consist indelivering a mass of milk onto an evaporat ng surface in oacuo heated in excess of five degrees centigrade above the boiling point of the vacuo and to a temperature a proximating ninety-eight degrees centigra e, and then removing the said milk in the form of a self-sustaining mass having the identity of a film from said surface while in such a condition that it has a moist appearance and its moisture-content when dry and coolis between one and one-half and five and one-half per cent.

9. In the process of desiccating the solidcontent of milk, the steps which consist in delivering a mass of milk onto an evaporatin surface in oacuo heated in excess of five egrees centigrade above the boiling point of the oacuo and in excess of seventyfive degrees centigrade, and sufiiciently high to sterilize said milk, and then removing the said milk in the form of a self-sustaining mass having the identity of a film from said surface while in such a condition that it has a moist appearance and its moisture content when dry and cool is between two and one-half and five and one-half per cent.

10. In the process of desiccating the solidcontent of milk, the steps which consist in delivering a mass of milk onto an evaporating surface in 'uacuo heated in excess of five degrees centigrade above the boiling point of the vacuo and in excess of seventy-five degrees centigrade, and sufficiently high to sterilize said milk and then removing said milk in the form of a self-sustaining mass having the identity of a film from said surface while in such a condition that it has a moist appearance and its moisture-content when dry and cool is between two and onehalf and four per cent.

11. In the process of desiccating the solidcontent of milk in eacuo by contact with a moving surface heated in excess of five degrees centigrade above the boiling point of the cacao, the steps which consist in conveying a mass of milk from the source of supply while under pressure of at least'at- I mospheric, through a covered conduit into a receptacle of relatively large superficial content; then maintaining a cacao immediately above the relatively large exposedsurface of the milk in said receptacle, while maintaining same out of direct contact with drawing a a moving evaporating surface heated in excess of five degrees centigrade above the boiling point of the ammo, whereby expansion of said milk prior to contact with said surface is permitted, and then delivering said milk onto said moving surface while the latter is heated in excess of'five degrees centigrade above the boiling point of the milk 1n said 'vacuo, and then removing said milk in the form of a self-sustaining mass having the identity of a film'from said surface in such a conditlon that its moisturecontent when dry and cool is in excess of one and one-half per cent.

12. The process of desiccating the solidcontent of milk, which consists in rapidly concentrating a body of milk in 'vacuo, withhomogeneously concentrated layer therefrom, while effecting a transfer of heat units from the outer surface of said layer to inflowing milk in close proximity thereto and out of contact therewith, delivering the said layer onto a surface heated in excess of five de rees centigrade above the boiling point 0 the ammo, and removing said milk in the form of :1 self-sustaining mass having the'identity of a film from said surface in such a condition that its moisture-content, when dry and cool is in excess of one and one-half per cent.

13. In the process of desiccating the solidcontent of milk, the steps which consist in delivering a mass of milk onto an evaporating surface in vacuo heated in sufiicient excess of the boiling point of the 'vacuo to effect rapid vaporization of the liquid-content of said mass, and then removing said milk in the form of a self-sustaining mass having the identity of a film from said surface while in such condition that it has a moist appearance, and its moisture content when dry and cool is in excess of one and one-half per cent.

14. In the process of desiccating the solidcontent of milk, the steps which consist in delivering a mass of milk onto an evaporating surface in vacuo heated in suflicient excess of the boiling point of the vacuoflto efiect rapid vaporizatlon of the liquid-content of said mass, and then removing said milk in the form of a self-sustaining mass having the identity of a' film from sald surface while in such condition that it has a moist appearance, and its moisture content when dry and cool is between one and onehalf and five and one-half per cent.

15. In the process of desiccating the solidcontent of milk, the ste s which-consist in delivering a mass of mil r onto an evaporating surface in vacuo heated in suflicient excess of the boiling point of the 'vacuo to effect rapid vaporization of the liquid-content of said mass, and then removing said milk in the form of a self-sustaining mass having the identity of a film from sald surface while in such condition that it has a moist appearance, and its moisture content when dry and cool is between two and onehalf and four per cent.

In testimony whereof I aflix my signature in presence of two witnesses.

WAITSTILL H. SWENARTON.

Witnessesz' EUGENE G. BROWN, JULIA B. HILL. 

